Your friend wasn’t banned because they weren’t caught. You, however, were.
It’s a common rule across every server that the use of hacked clients is forbidden.
I would advise you to keep such clients off multiplayer servers and automatically assume that they are a bannable offense.
Can you read the rules and quote the rule(s) you broke? Please respond in a new message, don’t edit your appeal. If you do not know how to quote the rules, read the guide How to quote the rules.
If you do not identify the right rule(s) that you broke or you do not know which ones you broke, I can make it clear.